Comparison of electrostatic- and hydrophobic-induced pKa shifts in polypentapeptides. The lysine residue

✍ Scribed by Dan.W. Urry; Shaoqing Peng; D.Channe Gowda; Timothy M. Parker; R.Dean Harris

• Book ID: 103030344
• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 657 KB
• Volume: 225
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(94)00612-1

✦ Synopsis

Acid-base titrations at 37°C determined the PK. values in water and saline of twelve synthesized polypentapeptides, polycfv(GVGIP),fn(GKGIP) ), where&+&= 1 with& ranging from 1 to 0.06 and where K is the lysine (NH: /NH,) residue.

In water the p& was 9.60 nearfx=0.9 decreasing to 9.20 at&= 1 and to 8.18 at&= 0.06. At 37°C in the NH2 state, the polymers form a viscoelastic phase of 5096 water by volume where for 1;(= 0 previous dielectric permittivity data place the dielectric constant near 65. For fncO.9 the decrease in pK, could not be explained by the usual electrostatic self-energy argument of decreased dielectric constant as Lys (K) is replaced by Val (V). Instead, an apolar-polar repulsive free energy of hydration is discussed which provides a basis for hydrophobic-induced pX; shins.